British Patent Specification No. 2,032,559 discloses a method of repairing a defective tube in a tube-in-shell heat exchanger which avoids plugging the tube and which consists of inserting a tubular sleeve within the defective tube and sealingly bonding the end regions of the sleeve to the tube and the tube sheet to bridge the defect. The means of sealingly bonding the sleeve included brazing both end regions, or brazing one end region of the sleeve to the tube and explosively welding the other end region of the sleeve to the tube sheet.
It is obviously more convenient from a practical point of view to employ similar sealing techniques for both end regions of the sleeve. Explosive welding is a technique which has proved to be effective and consistent in this context, whilst brazing, though generally effective, is less easy to perform in a reliable and consistent manner. It is therefore an object of the invention to provide a method whereby explosive welding can be applied to the sealing of the repair sleeve to the heat exchanger tube whilst being disposed therewithin.
The main problem involved in the application of such a sealing technique is the lack of support against the radially outward force generated by the explosion, contrasted with the situation at the other end of the repair sleeve where the mass and dimensions of the tube sheet provide a more than adequate self-support. The proximity of the heat exchanger tubes in a typical array makes it almost impossible to provide a temporary fully radial support which can be assembled and removed easily and rapidly.